A micro fuse is a device to protect electronic elements by interrupting excessive electrical current in an electronic circuit. It is an essential component in an electronic device such as a mobile electronic device or a charger. With increasing use of mobile electronic devices and chargers therefor, surface mount device (SMD)-type micro fuses that can stably operate at high surges have been developed and used.
Categories of micro fuses include fast-acting fuses for overcurrent and time-lag fuses for inrush current or high surges.
A time-lag micro fuse is designed such that the length of a fuse wire (fusible element) is longer than that in a normal fuse. Korean Patent No. 10-1058946, which is issued to the present assignee and titled “Time-lag Micro Fuse with Multilayered Molding Layer and Method for Manufacturing the Same”, suggests a micro fuse including a fuse substrate, a fusible element connected to each terminal formed on the fuse substrate, and a molding layer formed on the entire surface of the fuse substrate to cover the fusible element.
Recently, with development of smart mobile electronic devices such as table computers and mobile telecommunication devices, there is the demand for electricity storage devices having high capacity. Therefore, there is a trend wherein high-capacity secondary batteries such as Li-ion and Li-polymer batteries are being developed. Along with such trends, there is also demand for development of a fuse having a thermal fuse function due to risk of fire or explosion during battery charging or discharging at high temperatures, in addition to the usual current fuse function that deals with overcurrent higher than rated current.